Power module package having excellent heat sink emission capability and method for manufacturing the same

ABSTRACT

A power module package includes a power circuit element, a control circuit element, a lead frame, an aluminum oxide substrate having a heat sink and an insulation layer, and a sealing resin. The control circuit element is electrically connected with the power circuit element to control chips within the power circuit element. The lead frame has external connection terminal leads in its edge and has a first surface to which the power circuit element and the control circuit element are attached and a second surface which is used as a heat transmission path. The heat sink is a plate made of metal such as aluminum and the electrical insulation layer is formed at least on an upper surface of the heat sink and made of aluminum oxide. The electrical insulation layer may be formed over an entire surface of the heat sink. Here, the insulation layer is attached to the second surface by an adhesive, on a region below where the power circuit element is attached, to the first surface of the lead frame. In addition, the sealing resin encloses the power circuit element and the control circuit element, the lead frame, and the metal oxide substrate and exposes the external connection terminals of the lead frame.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/565,274 filed Sep. 23, 2009, which is a continuation of U.S. patentapplication Ser. No. 11/208,385 filed Aug. 19, 2005, which claimspriority to Korean Patent Application No. 2004-66176, filed on Aug. 21,2004, in the Korean Intellectual Property Office and is also acontinuation-in-part of U.S. patent application Ser. No. 10/167,067,filed Oct. 26, 2004, now U.S. Pat. No. 7,061,080, which claims priorityto Korean Patent Application No. 2002-20779, filed on Apr. 17, 2002 inthe Korean Intellectual Property Office and Korean Patent ApplicationNo. 2001-32489, filed on Jun. 11, 2001, in the Korean IntellectualProperty Office. All of the above-listed applications are herebyincorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor package, and moreparticularly, to a power module package having excellent heat transfercharacteristics.

2. Description of the Related Art

Generally, a semiconductor package is manufactured in the following way:one or more semiconductor chips, such as power semiconductor devices orintegrated circuits, are mounted on a lead frame or a printed circuitboard (PCB), then sealed with an epoxy molding compound (EMC) forprotecting the chips, and the packaged chips are mounted on a motherboard or a PCB for a system. As used hereinafter the word “chip” means asemiconductor power device or a semiconductor integrated circuit. Asemiconductor power device may be a single power transistor or one ormore power transistors including one or more transistors for controllingor monitoring operation of the power transistors.

While integrated circuits and other electronic apparatus have longexperienced demands for high speed, high capacity, and high levels ofintegration, now power devices such as those applied to automobiles,industrial apparatus, and home appliances are also confronting similardemands for reduced size, lower weight and low cost. One way ofresolving these demands is to construct a power module package thatcontains two or more semiconductor chips in a single semiconductorpackage. Such power module packages include one or more power circuitchips and a control circuit chip. But power circuit chips generate muchmore heat than the heat generated by integrated circuits or controlchips. Therefore, effectively transferring heat from the chips tooutside the package is critical for maintaining high reliability for along time for such power modules.

The U.S. Pat. No. 5,703,399 by Majumdar, entitled “Semiconductor powermodule” discloses a power module package having a heat sink and FIG. 1herein illustrates a cross-sectional view of the power module packageshown in that patent. Referring to FIG. 1, the power module package 10mounts a plurality of semiconductor chips constituting a power device 9and a control device 8 on a lead frame 3 that has a heat sink 1 belowthe lead frame 3. The package shown In FIG. 1 has two types of EMC.Reference numeral “2” represents a “lower EMC” having excellent thermalconductivity and ordinary electrical insulation and upper EMC 7 hasordinary thermal conductivity and excellent electrical insulation. Thepower circuit chip 4 a is mounted on one side of the lead frame 3 and acontrol integrated circuit chip 5 a is mounted on the same side of thelead frame 3 and spaced from the power chip 4 a. Reference numerals 5 b,6 b and 6 a represent, respectively, a resistance component, a goldwire, and an aluminum wire. In the power module package 10 having theconstruction as described above, heat generated from the power circuitchip 5 a is mostly delivered to the heat sink 1 through lower EMC 2 andthen to outside the power module package 10 through the heat sink 1.According to the above United States patent, the heat sink 1 is made ofa metal having high thermal conductivity such as copper or aluminum.

When, as in the package 10 where the heat sink 1 is manufactured usingelectrically conductive material such as metal, the lower EMC 2 shouldsatisfy the following two conditions. First, heat transferred from thepower circuit chip 4 a should be transferred quickly to the heat sink 1.Second, the lead frame 3 should be electrically insulated from the heatsink 1.

To satisfy these conditions, the above United States patent uses an EMCwith high thermal conductivity for the lower EMC 2. However, even thoughthe EMC has high thermal conductivity, its thermal conductivity is 2W/m·K, which is much less than the thermal conductivity of an aluminumheat sink 1 whose thermal conductivity is 100 W/m·K. In order to providesufficient electrical insulation between the heat sink 1 and the leadframe 3, the lower EMC 2 should be at least 500 μm thick or more so thatthe lead frame may be insulated from the heat sink 1. If the EMC 2 ismuch thinner, then one or both devices 4 a, 5 a may short circuit to theheat sink 1 and damage or destroy the power module 10. As such, the heatsinking ability of the power module package 10 is limited by the lowerEMC 2.

The power module package 10 uses two EMCs 2 and 7 and each has differentproperties. Those skilled in the art understand that there is often atradeoff between the electrical insulating ability of a molding compoundand its thermal conductivity. In general, as one increases, the otherdecreases. So, in the package 10 that requires an EMC having highelectrical insulation for the upper EMC, a two-stage molding process isperformed. Accordingly, a manufacturing process of the power modulepackage 10 is complex and costly. One way of solving the above problemand using only one EMC is shown in Korean Patent Publication No.2002-0095053, filed by the same applicant as the present invention, andentitled “Power module package having improved heat emission capabilityand method thereof.” FIG. 2 herein illustrates a schematic,cross-sectional view of an example of the power module package 100suggested by the above Korean Patent Publication.

Referring to FIG. 2, the power module package 100 mounts a power circuitelement 120 and a control circuit element 130, both on a first surface111 of the lead frame 110. The power circuit element 120 is mounted on adown-set (recessed) die pad 140 of the lead frame 110. A heat sink 150is attached to a second surface 112 of the down-set die pad 140 by ahigh temperature tape 160. In FIG. 2, reference numerals 121, 122, 130,132, and 170 represent one or more power circuit chips, an aluminumwire, a control circuit chip, a gold wire, and an EMC, respectively.

In the power module package 100, a heat sink 150 made of ceramic isdirectly attached to a backside of a down-set die pad 140 by a hightemperature tape 160. The high temperature tape 160 can be as thin asabout 50 μm. Since the sealing process for the power module package 100is performed using only one EMC 170, the manufacturing process for thepackage shown in FIG. 2 is simpler than the process for the package ofFIG. 1 and the process to make the package of FIG. 2 can be automated tofurther reduce cost.

However, the ceramic heat sink 150 has a thermal conductivity of about24 W/m·K, so that its heat sinking ability is not as good as metal, andfurther, ceramic is more expensive than metal. Still further, there islimit on how thin one can make a ceramic heat sink because ceramic isbrittle and will crack if it is too thin.

FIG. 3 illustrates a cross-sectional view of another example of a powermodule package 200 disclosed in the above-described Korean PatentPublication No. 2002-0095053. Referring to FIG. 3, the power modulepackage 200 uses a direct bonded copper (DBC) substrate 250. The DBCsubstrate 250 includes: a ceramic plate 251 at the center; an uppercopper layer 252 attached to an upper surface of the ceramic plate 251;and a lower copper layer 253 attached to a lower surface of the ceramicplate 251. One or more power circuit chips 221 are mounted on the uppercopper layer 252 and the lower copper layer 253 acts as a heat sink ofthe power module package 200. Reference numerals 210, 222, and 270represent a lead frame, an aluminum wire, and EMC, respectively.

According to the power module package 200, the upper and the lowercopper layers 252 and 253 are directly attached to the ceramic plate 251without using EMC (refer to the reference numeral 2 in FIG. 1) or a hightemperature adhesive (refer to the reference numeral 160 in FIG. 2) andthe heat dissipation capability of the heat sink 250 is excellent thanksto high thermal conductivity of copper. Further, since the copper layers252 and 253 are attached to the upper and lower surfaces of the ceramicplate, problems caused by brittleness of the ceramic are overcome. Stillfurther, since the encapsulation process for the power module package200 is performed in a single transfer molding process using one EMC 270,its manufacturing process can be simplified and automated to reducecosts.

However, the ceramic plate 251 of DBC substrate 250 still has a lowerthermal conductivity than metal and the ceramic plate 251 is still about635 μm thick so that the manufacturing cost of the DBC process is high.As such, there is still substantial room for reducing the size andimproving thermal dissipation ability of the power module package 200.

SUMMARY OF THE INVENTION

The present invention provides a power module package and amanufacturing method thereof, with excellent heat dissipation abilityand a simpler and lower cost method of automated manufacture.

According to one aspect of the present invention, there is provided apower module package and a manufacturing method thereof, capable ofreducing manufacturing costs and reducing the thickness of a substrateor a heat sink so that it has appropriate characteristics for a powermodule package. The invention includes a heat sink that has a core orcentral element made of metal and a one or more electrical insulatinglayers comprising a compound of the metal and one or more otherelements, in particular, an oxide of the metal on the core or centralelement.

According to another aspect of the present invention, there is provideda power module package, which includes: a power circuit element; acontrol circuit element; a lead frame; a metal oxide substrate; and anEMC. The control circuit element is connected with the power circuitelement to control operation of the power circuit element. The leadframe has external connection terminal leads in its edge and has a firstsurface to which the power circuit element and the control circuitelement are attached and a second surface used to transfer heat awayfrom the chips. A metal/metal oxide substrate, e.g., analuminum/aluminum oxide substrate acts as a heat sink and an insulationlayer. The heat sink is a plate made of aluminum and the electricalinsulating layer is formed at least on an upper surface of the heat sinkand made of the aluminum oxide. The aluminum oxide layer is anelectrical insulating layer that is affixed to the lead frame by anadhesive or other suitable means. The aluminum oxide layer covers all orat least part of the second surface of the lead frame below a regionwhere the power circuit element is attached. The EMC encloses the powercircuit element, the control circuit element, the lead frame, and themetal/metal oxide substrate and exposes the external connection terminalof the lead frame.

According to further another aspect of the present invention, there isprovided a power module package, which includes: a metal/metal oxidesubstrate; an upper wiring layer; external connection terminal leads; apower circuit element; a control circuit element; and an EMC. Themetal/metal oxide substrate includes: a heat sink of a plate made ofmetal, e.g., aluminum and an electrical insulation layer formed at leaston an upper surface of the heat sink and made of an oxide of the metal,in particular, aluminum oxide. An upper wiring layer has a wiringpattern and is directly attached to an upper surface of the insulationlayer. The external connection terminal leads are connected at one oftheir ends with an edge of the wiring pattern of the upper wiring layer.The power circuit element is attached to a surface of the upper wiringlayer adjacent the leads and is electrically connected with the externalconnection terminal leads by means of bond wires. The control circuitelement is attached to a surface of the upper wiring layer and adjacentother external connection terminal leads. The control circuit element iselectrically connected with the power circuit element and to theexternal connection terminal leads through a wiring bonding pattern tocontrol the power circuit element(s). The EMC encloses the power circuitelement(s), the control circuit element, the upper wiring layer, themetal oxide substrate, the inner ends of the external connectionterminals, the internal bond wires, and exposes the outer ends of theexternal connection terminals.

According to still further another aspect of the present invention,there is provided a power module package, which includes: a metal/metaloxide substrate; a first wiring layer; a second wiring layer; externalconnection terminals; a power circuit element; a control circuitelement; and an EMC. The metal/metal oxide substrate includes: anelectrical insulation layer made of an oxide on a metal plate. Aplurality of vias are made that comprise the metal within the electricalinsulation layer. The vias pass through the insulation layer. A firstwiring layer has a first wiring pattern connected with one end of thevias and is directly attached to a first surface of the metal/metaloxide substrate. The second wiring layer has a second wiring patternconnected to the other end of the vias and is directly attached to asecond surface of the metal/metal oxide substrate. The externalconnection terminal leads are connected at their inner ends to an edgeof the first wiring pattern of the first wiring layer. The power circuitelement is attached to a surface of the second wiring layer andelectrically connected with the via through the second wiring pattern.The control circuit element is attached to a surface of the first wiringlayer between the external connection terminal leads and is electricallyconnected with the via and the external connection terminal leadsthrough the first wiring pattern to control chips within the powercircuit element. The EMC encloses the power circuit element, the controlcircuit element, the first wiring layer, the second wiring layer, themetal oxide substrate, and one end of the external connection terminals,exposing the other end of the external connection terminals.

According to one aspect of the above-described embodiment, all or partof one surface of the electrical insulation layer of the heat sink maybe exposed to an outside of the EMC.

According to another aspect of the present invention, there is provideda power module package, which includes: a metal/metal oxide substrate; acase; an upper wiring layer; external connection terminal leads; a powercircuit element; a control circuit element; and silicone. Themetal/metal oxide substrate includes: a heat sink of a plate made ofmetal and an electrical insulation layer formed at least on an uppersurface of the heat sink and made of an oxide of the metal. The caseincludes: sidewalls with bottom edges attached to an edge of the metaloxide substrate and a cap connected between the top edges of thesidewalls so as to define a predetermined space between the sidewalls.The upper wiring layer has wiring pattern and is directly attached to anupper surface of the insulation layer between the sidewalls. Theexternal connection terminal leads are connected at their inner endswith the wiring pattern of the upper wiring layer and are exposed attheir outer ends for connection to the rest a device or system. Thepower circuit element is attached to a surface of the upper wiring layerand electrically connected with the external connection terminal leadsthrough the wiring pattern. The control circuit element is attached to asurface of the upper wiring layer and electrically connected with thepower circuit element and the external connection terminal leads throughthe wiring pattern to control the power circuit element. A siliconeresin fills a space of the case so as to seal up the power circuitelement, the control circuit element, and the upper wiring layer.

According to another aspect of the present invention, there is provideda semiconductor package, which includes: a metal/metal oxide substrate;a wiring pattern; an external connection pad; a semiconductor chip; andan EMC. The metal/metal oxide substrate includes an insulation layer andvias made of an oxide of a plate-shaped metal and of the vias are madeof the metal embedded in the insulation layer, and passing through theinsulation layer. A wiring pattern is formed on the first surface of themetal oxide substrate and is connected with one of the ends of the vias.An external connection pad is formed on the second surface of themetal/metal oxide substrate and is connected with the other ends of thevias. The semiconductor chip, e.g., a power circuit chip is electricallyconnected with the wiring pattern through a contact bump and is mountedon the first surface of the metal oxide substrate. EMC encloses thepower chip and the first surface of the metal oxide substrate butexposes the second surface of the metal oxide substrate.

According to another aspect of the present invention, there is provideda method for manufacturing a power module package, in which: a leadframe having external connection terminals in its edge is provided, aheat sink of a plate made of metal is oxidized to form an electricalinsulation layer on at least on an upper surface of the metal plate; apower circuit chip and a control chip are attached to a first surface ofthe lead frame; the lead frame is attached to the metal oxide substrateso that the insulation layer is affixed at least on a region of a secondsurface of the lead frame that corresponds to a region on the firstsurface where the power circuit element is attached; a wire bondingoperation is performed to connect one or more power circuit chips and acontrol circuit chip; and encapsulating using an EMC to encapsulate thepower circuit element(s), the control circuit element, the lead frame,and the metal/metal oxide substrate and expose the external connectionterminal leads.

According to another aspect of the present invention, there is provideda method for manufacturing a power module package, in which: ametal/metal oxide substrate including a heat sink of a plate made ofmetal and an insulation layer formed at least on an upper surface of themetal plate heat sink and made of an oxide of the metal are prepared forattachment to the lead frame; an upper wiring layer having a wiringpattern is attached to an upper surface of the insulation layer; innerends of external connection terminal leads are attached to an edge ofthe wiring pattern of the upper wiring layer; one or more power circuitchip(s) and a control circuit chip are attached to a surface of theupper wiring layer adjacent the inner ends of the external connectionterminal leads; wire bonding is performed to connect the power circuitchip(s) and the control circuit chip; encapsulating using an EMC toenclose the power circuit element(s), the control circuit element, theupper wiring layer, the metal oxide substrate, and one end of theexternal connection terminals and expose the other end of the externalconnection terminals.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a schematic, cross-sectional view of one example of a powermodule package according to a related art;

FIG. 2 is a schematic, cross-sectional view of another example of apower module package according to a related art;

FIG. 3 is a schematic, cross-sectional view of still another example ofa power module package according to a related art;

FIG. 4 is a schematic, cross-sectional view of a power module packageaccording to a first embodiment of the present invention;

FIG. 5 is a schematic, cross-sectional view of a power module packageaccording to a second embodiment of the present invention;

FIG. 6 is a schematic, cross-sectional view of a power module packageaccording to a third embodiment of the present invention;

FIG. 7 is a schematic, cross-sectional view of a modification of a powermodule package according to a third embodiment of the present invention;

FIG. 8 is a schematic, cross-sectional view of a power module packageaccording to a fifth embodiment of the present invention;

FIG. 9 is a schematic, cross-sectional view of one example of asemiconductor package according to the present invention;

FIGS. 10A through 10D are cross-sectional views explaining a method formanufacturing a power module package according to an embodiment of thepresent invention; and

FIG. 11 is a flowchart explaining a method for manufacturing a powermodule package according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully with reference tothe accompanying drawings, in which exemplary embodiments of theinvention are shown. Those of ordinary skill in the art will understandthat other arrangements of power circuit elements and control circuitelements described in the specification are possible and the structuresof a lead frame and a heat sink herein are exemplarily and not limitedto the specific arrangements or shapes as illustrated in the drawings.

FIG. 4 is a schematic, cross-sectional view of a power module packageaccording to a first embodiment of the present invention.

Referring to FIG. 4, a power module package 300 includes: a lead frame310; a power circuit element 320; a control circuit element 330; ametal/metal oxide substrate 350, 355; and an EMC 370.

The power circuit element 320 includes one or more power circuit chips321 with aluminum wire 322 to connect the chips 321 to the leads of thelead frame. The aluminum wire 322 has a diameter of about 250-500 μm toendure a high rated current. The control circuit element 330 includes acontrol circuit chip 331 and a gold wire 332. The aluminum wires 322 andthe gold wires 332 properly connect the power circuit chip(s) 321 andthe control circuit chip 331, respectively to the leads of the leadframe 310 that extend from inside the package 300 to the outside.

The lead frame 310 has a thickness of about 0.5-1 mm and has a firstsurface 311 on which the circuit elements are attached and a secondsurface 312 which is opposite to the first surface. External connectionterminal leads are formed at an edge of the lead frame 310. The externalconnection terminal leads have inner ends adjacent to the circuitelements and outer ends that protrude through the EMC 370. A down-setdie pad 340 is formed at a central portion. The circuit elements 320 and330 may be attached to a die pad in the same plane as the leads or to adown-set die pad, such as die pad 340. The down-set die pad 340 may bepositioned on a symmetric central point or may be formed at an eccentricposition. The power circuit element 320 and the control circuit element330 are attached to the first surface 311 of the lead frame.Particularly, the power circuit element 320 which generates most of theheat is attached to the first surface 311 of the down-set die pad 340 ofthe lead frame 310.

The metal oxide substrate 350, 355 is attached by an adhesive 360 to thesecond surface 312 of the lead frame 310 at a location that correspondsto the region on the first surface where the power circuit element 320is attached. As illustrated in FIG. 4, the metal oxide substrate 350 and355 may be attached to the second surface 312 of the down-set die pad340 of the lead frame 310.

The adhesive 360 is an epoxy adhesive or silicone elastomer. A fillerhaving excellent thermal conductivity and substantial electricinsulation may be dispersed in the adhesive 360. For the filler,aluminum nitride (AlN), aluminum oxide (Al₂O₃), beryllium oxide (BeO),silicon oxide (SiO₂), or combination thereof may be used. For theadhesive 360, a high temperature tape or solder for a high temperaturemay be used, such as Pb/Sn, Sn/Ag, Pb/Sn/Ag. The adhesive 360 may beformed thin within a thickness of about 10-20 μm so that thermalconductive efficiency will not deteriorate but the thickness of theadhesive 360 is not limited to that thickness.

The metal/metal oxide substrate 350, 355 includes a heat sink 350 and aninsulation layer 355 made of an oxide of the metal of the heat sink 350.The heat sink 350 effectively conducts heat generated from the powercircuit element 320 to the outside of the package 300. For the heat sink350, material having an excellent conductivity is used and aluminumhaving a thermal conductivity of about 100-130 W/m·K is preferred. Thereis no limitation in thickness of the heat sink 350 and the thickness canbe modified in various ways depending on a purpose of the power modulepackage 300. Of course, other metal and metal oxide combinations arepossible, e.g. Si and SiO₂.

The electrical insulation layer 355 should not only electricallyinsulate the lead frame 310 from the heat sink but also guarantee rapidheat transmission to the heat sink 350. Therefore, the layer 355 may bemade of material having an excellent thermal conductivity and showing asufficient electrical insulating ability that it can be made as thin aspossible. For that purpose, the insulation layer 355 is made of an oxideof metal of the heat sink 350 such as an aluminum oxide. The aluminumoxide insulation layer 355 has a thermal conductivity of about 20 W/m·K,which is greater than the thermal conductivity the lower EMC 2 (inFIG. 1) or the adhesive 360. Further, the aluminum oxide insulationlayer 355 has an excellent electric insulation property as does ceramicmaterial. Therefore, the insulation layer, particularly, an insulationlayer 355 a interposed between the lead frame 310 and the heat sink 350can display a full electrical insulating effect even with a thickness ofonly about 30-50 μm. The thickness of the insulation layer 355 a,however, may change depending on electric properties of the applicationapparatus for which the power module package 300 is used.

The electrical insulation layer 355 is formed at least on an uppersurface of the heat sink 350. For example, the insulation layer 355 maybe formed on only an upper surface of the heat sink 350 (refer to thereference numeral 355 a), or may be formed on only an upper and a lowersurfaces of the heat sink 350 (refer to the reference numerals 355 a and355 b), or may be formed over an entire surface of the heat sink 350(refer to the reference numerals 355 a, 355 b, 355 c). The metal/metaloxide substrate 355 may be formed by anodizing metal 350 that would beused as the heat sink 350. When the electrical insulation layer 355 on apartial surface of the heat sink 350, an oxidation operation isperformed with the rest surface of the heat sink 350 masked. When theinsulation layer 355 is formed over the entire surface of the heat sink350, the manufacturing operation becomes simple and the hardness of themetal oxide substrate 350 and 355 is increased and thermal property ofthe power module package 300 is improved. When forming the insulationlayer 355 a on only the upper surface or forming the insulation layers355 a and 355 b on only the upper surface and the side of the heat sink350, a heat transmission property of the power module package 300 isalso improved.

The EMC 370 is intended to maintain an electrical insulation statebetween the elements 320 and 330 by isolating the power circuit element320 and the control circuit element 330 from each other and by isolatingboth of them from the outside. The EMC 370 may be formed using an epoxymolding compound having an excellent insulating property. In that case,the EMC 370 encloses the power circuit element 320, the control circuitelement 330, the lead frame 310, and metal oxide substrate 350 and 355,exposing the outer ends of external connection terminal leads of thelead frame 310. To improve a heat transmission, the EMC 370 may exposeone side of the metal/metal oxide substrate 355 to the outside.

According to the above-described power module package 300 has analuminum heat sink which has an excellent heat conductivity and thealuminum oxide which has relatively good thermal conductivity andelectrically insulates the aluminum 350 from the lead frame 310.

FIGS. 10A through 10D are cross-sectional views explaining an example ofa method for manufacturing a power module package 300 according to afirst embodiment of the present invention.

First, referring to FIG. 10A, a lead frame 310 having a thickness ofabout 0.5-1.0 mm is prepared. Power circuit chip(s) 321 and a controlcircuit chip 331 are attached to a surface of the lead frame 310 througha die attach operation. The power circuit chip(s) 321 are attached to adown-set die pad portion 340 of the lead frame 310. The die attachoperation can be performed using solder or using silver epoxy. Whensolder is used for an adhesive (not shown), the die attach operation isperformed within a temperature range of about 350-380° C., a pressurerange of about 3-5 kg/cm², and in a hydrogen atmosphere. When silverepoxy is used for an adhesive, the die attach operation is performed atroom temperature and at a pressure range of 1-2 kg/cm².

Next, referring to FIG. 10B, oxidizing one or more surfaces of analuminum plate 350 to provide aluminum oxide layers 355 a, 355 b, 355 c.An adhesive 360 such as an epoxy or a silicone elastomer, including afiller is attached to an upper surface of the insulation layer 355 a.

Next, referring to FIG. 10C, the aluminum/aluminum oxide substrate 355is attached to the lower surface of lead frame 310, at a position belowthe location where power circuit chip(s) 321 are attached to the uppersurface, using the epoxy 360 including the filler for an adhesive. Theabove attach operation may be performed under a temperature range ofabout 150-180° C. and a pressure range of 0.5-1.0 kg/cm² for about 3-5minutes but is not limited to those specific ranges.

Referring to FIG. 10D, an aluminum (Al) wire bonding operation and agold (Au) wire bonding operation are performed so that the power circuitchip 321 is electrically connected with the lead frame 310 and the powercircuit chips 321 are electrically connected each other, and the controlcircuit chip 330 is electrically connected with the lead frame 310.Generally, a gold wire is used as a wire for the control circuit chip330 and an aluminum wire is used as a wire for the power circuit chip321. The aluminum wire bonding operation is performed using a wedgebonding method and the gold wire bonding operation is performed using aball bonding method. For a swift wire bonding operation, the aluminumwire 332 is bonded first and subsequently the gold wire 332 is bonded.

Subsequently, referring to FIG. 4, an encapsulation operation such as atransfer molding method is performed to enclose the circuit elements 320and 330 so that only a lower surface of the aluminum/aluminum oxidesubstrate 355 and the outer ends of the leads may be exposed. Afterthat, general subsequent operations such as a trimming and a forming areperformed.

FIG. 5 is a cross-sectional view of a power module package according toa second embodiment of the present invention. The power module package400 of the present embodiment is different from the power module package200 of the prior art in that it uses the metal/metal oxide substrate 455having an upper wiring layer 452 on its upper part, not the DBCsubstrate (refer to a reference numeral 250 in FIG. 3) includingceramic. A difference between the power module package 300 of theabove-described first embodiment and that of the related art will bedescribed in more detail.

Referring to FIG. 5, the power module package 400 according to the firstembodiment includes: a lead frame 410; one or more power circuitelements 420; a control circuit element 430; an upper wiring layer 452;an aluminum/aluminum oxide substrate 455; and an EMC 470. The powercircuit element(s) 420 include power circuit chips 421 and aluminum/goldwire 422. The control circuit element 430 includes a control circuitchip 431 and aluminum/gold wire 432. The aluminum/aluminum oxidesubstrate 450, 455 includes heat sink 450 and an insulation layer 455 aformed at least on an upper surface of the heat sink 450. As illustratedin FIG. 5, the insulation layer 455 a may be formed over an entiresurface of the heat sink 450. See layer 455 b (lower) and 455 c(sidewalls).

The upper wiring layer 452 has a wiring pattern for leads (not shown)and regions between leads are filled with insulating material. Theinsulating material may be part of the EMC 470. The power circuit chip421 and the control circuit chip 431 are attached to a surface of theupper wiring layer 452 and the aluminum/gold wire 422 and thealuminum/gold wire 432 are connected to the leads of the wiring patternof the upper wiring layer 452. The upper wiring layer 452 is directlyattached to a surface of the upper insulating layer 455 a of thealuminum oxide layer 455. The wiring pattern of the upper wiring layer452 connects the power circuit elements 420, connects the lead frame 410with the power circuit element 420, and electrically connects the powercircuit element with the control circuit element 430.

In the power module package 400 having the above-described structure,the heat sink 450 has excellent thermal conductivity and acts as a heatsink and the aluminum oxide 455 a, 455 b, 455 c is an excellent thermalconductor and a relatively excellent electric insulator. Further, theupper wiring layer 452 is directly attached to a surface of the upperinsulation layer 455 a of the metal/metal oxide substrate 455 to thatheat transmission is increased even more.

FIG. 11 is a flowchart explaining an example of a method formanufacturing a power module package according to a second embodiment ofthe present invention.

First, aluminum/aluminum oxide substrate 455 is prepared (S21). Thealuminum/aluminum oxide substrate 455 includes the heat sink 450 and atleast one insulation layer 455 a made of the aluminum oxide and formedat least on an upper surface of the heat sink 450. The insulation layer455 a may be formed over an entire surface of the heat sink 450. Thealuminum/aluminum oxide substrate 455 may be manufactured by performinga general aluminum oxidation operation known or anodizing. Suchanodizing processes are well known.

The upper wiring layer 452 is directly formed on the insulation layer455 a (S22). The upper wiring layer 452 may be formed on the aluminumoxide layer 455 by a lamination method using Cu, Cu/Ni, Cu/Au, orCu/Ni/Au, or a sputtering method using the above metal. The upper wiringlayer 452 has a properly-shaped wiring pattern for electric connection.

Subsequently, the external connection terminal lead has its inner endsattached to an edge of the upper wiring layer 452 (S23). This attachoperation may be performed using an adhesive such as solder or a thermaltape, laser or spot welding, or using a thermal fusion method usingsilver (Ag) or silver (Ag)/stannum (Sn) plating. Next, the power circuitchip 421 and the control circuit chip 431 are attached to a surface ofthe upper wiring layer 452. The operation for attaching those chips 421and 431 can be performed using solder and silver epoxy. For attachingthe power circuit chip 421, solder is used. In that case, the attachoperation is performed within a temperature range of about 330-360° C.For attaching the control circuit chip 431, silver epoxy is used. Inthat case, the attach operation is performed under a room temperature.

Next, the wire bonding operation is performed (S24). For the powercircuit chip 421, an aluminum wire is used, and for the control circuitchip 431, a gold wire is used. The wire bonding operation may beperformed in the same way as the wire bonding operation of theabove-described manufacturing operation. As a result, the chips 421 and431 are electrically connected with the wiring pattern of the upperwiring layer 452.

After that, an encapsulation operation such as a molding operation isperformed using the EMC 470 (S25). In the encapsulation operation, atransfer molding method may be used. After general trimming and formingoperations are performed (S26), the power module package 400 asillustrated in FIG. 5 is completed.

FIG. 6 is a cross-sectional view of a power module package according toa third embodiment 500 of the present invention. In the thirdembodiment, only differences between package 500 and the first and thesecond embodiments will be described in detail. Referring to FIG. 6, apower module package 500 includes metal/metal oxide substrate 550, 558,a first wiring layer 552 a, a second wiring layer 552 b, externalconnection terminals 510, a power circuit element 520, a control circuitelement 530; and an EMC 570. The power module package 500 according tothe third embodiment is characterized by having a metal oxide substrate550 with vias 558 where the vias 558 pass through an insulation layer550 to electrically connect the first wiring layer 552 a with the secondwiring layer 552 b.

The metal/metal oxide substrate 550, 558 has an aluminum oxide substrate550 that has a planar configuration with a plurality of conductive vias558 in the substrate 550. The vias 558 pass through the insulation layer550. The conductive vias 558 may be formed using metal, e.g., aluminum.The aluminum/aluminum oxide substrate 550, 558 may be manufactured bymasking the via regions and oxidizing the rest of an aluminum metalplate. The unmasked portions will remain as aluminum.

The first wiring layer 552 a includes a first wiring pattern (not shown)and the first wiring pattern is connected to one of the ends of vias558. As an alternative, the first wiring pattern could be electricallyconnected with a control circuit chip 531 through external connectionterminals of the control circuit chip 531, such as a bump 532. Thecontrol circuit element 530 including the control circuit chip 531 andthe external connection terminals 532 are attached to a surface of thefirst wiring layer 552 a.

The second wiring layer 552 b includes a second wiring pattern (notshown) and the second wiring pattern is connected with the other ends ofthe vias 558. As an alternative, the second wiring pattern could beelectrically connected with the power circuit chip 521 through anexternal connection terminal of the power circuit chip 521, such as analuminum wire 522. The power circuit element 520 including the powercircuit chip 521 and the external connection terminal 522 is attached toa surface of the second wiring layer 552 b.

The external connection terminal 510 of the power module package 500,such as an external lead, is attached to an edge of the first wiringlayer 552 a that is electrically connected with the first wiringpattern. Alternatively, the external connection terminal 510 may beattached to an edge of the second wiring layer 552 b to be electricallyconnected with the second wiring pattern.

The power module package 500 dissipates less heat than the power modulepackages 300 and 400 according to the above-described first and secondembodiments. However, since the chips 521 and 531 are mounted on bothsides of the aluminum oxide substrate 550 and 558, module 500 has asmaller size than modules 300 and 400. Further, since the oxidizedaluminum insulation layer 550 has better heat conductivity than theprinted circuit boards (PCB) that are often used in a power modulesemiconductor package, it can be appropriately used as a power modulefor an application apparatus of relatively low power.

FIG. 7 is a cross-sectional view of a power module package 600 accordingto a fourth embodiment of the present invention. The package 600 is amodification of the third embodiment, package 500. Referring to FIG. 7,a power module package 600 includes metal/metal oxide substrate 650,658, a first wiring layer 652 a, a second wiring layer 652 b, externalconnection terminals 610, a power circuit element 620, a control circuitelement 630, and an EMC 670.

The power module package 600 according to the fourth embodiment isdifferent from the power module package 500 of the third embodiment inthat part of surface 650 a of the metal oxide substrate 650 is exposedoutside of the EMC 670. Although the power module package 500 accordingto the third embodiment with the insulation layer 550 has excellentthermal conductivity, the entire surface of the insulation layer 550 isenclosed by the EMC 570. Accordingly, when the power module package 500according to the third embodiment is used for a long time, its heatdissipation deteriorates. On the contrary, because the power modulepackage 600 of the fourth embodiment exposes part 650 a of the surfaceof the insulation layer 650, its heat dissipation efficiency is betterthan the power module package 500 of the third embodiment.

Referring to FIG. 7, opposite ends of the insulation layer 650 are bentvertically downward so that the left and right parts 650 a of thesurface of the electrical insulation layer 650 may be exposed to theoutside. However, the illustrated shape of the electrical insulationlayer 650 is a mere example. For example, the electrical insulationlayer 650 may have a bent portion forming an angle greater or smallerthan 90° or may have a straight portion with no bent portion.

FIG. 8 is a cross-sectional view of a power module package 700 accordingto a fifth embodiment of the present invention. Referring to FIG. 8, thepower module package 700 includes metal/metal oxide substrates 750, 755,a case 780, an upper wiring layer 752, external connection terminals710, a power circuit element 720, a control circuit element 730, and asilicone resin 770. The power module package 700 according to the fifthembodiment is similar in its structure to the power module package 400of the second embodiment except for the following differences.

Package 700 uses a silicone resin instead of an epoxy resin as anencapsulating resin 770 because the power module package 700 of thepresent embodiment is so large in its package area that the moldingoperation cannot be performed using the epoxy resin. In addition, due tothe fluent property of silicone resin 770, case 780 is provided so thata frame of the silicone resin may be maintained. The case 780 can bemanufactured using plastics.

The case 780 includes sidewalls 721-724 and a cap 720 and the sidewallsare attached at their bottom ends to an edge of the metal oxidesubstrates 750 and 755. The cap 720 is connected between the sidewalls721-724 to define a predetermined space between the sidewalls and thepredetermined space is filled with the silicone resin 770. The case 780may be attached to a surface of the metal oxide substrates 750 and 755using an adhesive or may be fastened to the surface of the metal/metaloxide substrates 750, 755 by inserting a fastening member such as a boltinto locking holes 782 formed on the metal oxide substrates 750 and 755and the case 780, respectively. A plurality of external connectionterminals 710 pass through the case 780 and are electrically connectedto the upper wiring layer 752.

The power module package 700 may house a high power device, such as aninsulated gate bipolar transistor (IGBT). The power module package 700is useful where the power device generates high heat. Further, in thepower module package 700 of the present embodiment having thealuminum/aluminum oxide substrates 750, 755 overcome the brittlenessproblem of the power module package having the DBC substrate including aceramic plate.

FIG. 9 is a cross-sectional view of one example of a semiconductorpackage 800 according to a sixth embodiment of the present invention.Referring to FIG. 9, a semiconductor package 800 includesaluminum/aluminum oxide substrate 855, 858, a wiring pattern 852 a,external connection pads 852 b, a semiconductor element 830, and asealing resin 870.

The semiconductor package 800 according to the sixth embodiment issimilar in its structure to a flip chip semiconductor package. Onedifference is that aluminum/aluminum oxide substrate 855, 858 includesan electrical insulation layer 855 made of a plate of aluminum oxide anda plurality of vias 858 made of non-oxidized aluminum that pass throughthe insulation layer 855. The aluminum/aluminum oxide substrate 855, 858can be formed by masking an aluminum plate and oxidizing the opposedaluminum to create the vias 858.

The wiring pattern 852 a connected with one end of the vias 858 isformed on a first surface of the aluminum/aluminum oxide substrate 855,858. A semiconductor chip 831 is mounted on the first surface andelectrically connected with the wiring pattern 852 a through the bump832. A solder resist 854 may be spread between the wiring patterns 852a. The external connection pads 852 b connected with the other end ofthe via 858 is formed on a second surface of the aluminum/aluminum oxidesubstrate 855, 858, which is an opposite side of the first surface. Asolder resist may be also spread between the external connection pads852 b. The external connection pads 852 b are attached to a mothersubstrate (not shown) using solder.

As described above, the semiconductor package having thealuminum/aluminum oxide substrate has a better heat transmissioncompared with the semiconductor package that uses a general PCB.

The power module package having the metal oxide substrate according tothe present invention uses metal having an excellent thermalconductivity as a heat sink and uses an oxide of the metal as anelectrical insulation layer so that the heat sink may be electricallyinsulated. The electrical insulation layer made of the oxide of suchmetal not only has a better thermal conductivity than the EMC resin butalso shows a sufficient insulation effect in case of forming a thicknessof the insulation layer thin. Therefore, according to the presentinvention, it is possible to manufacture the power module package havingan excellent heat emission property.

In addition, since the metal/metal oxide substrate provided to the powermodule package of the present invention can be manufactured by oxidizinga metal, the package can be easily realized and manufacturing cost isreduced. It is not necessary to perform the two-stage molding operationusing two sealing resins having different properties as was done in theprior art. Instead, the molding operation is performed using one sealingresin, so that the manufacturing process is less complex and may beautomated.

According to the present invention, it is possible to use thealuminum/aluminum oxide substrate having various thickness depending onpower capacity applied to the power module package and to modify itsstructure in various ways. Therefore, the power module package of thepresent invention can be applied to a package module having variouspower capacities.

Metal substrates with hard oxide metal coatings may be made by one ormore processes. Aluminum is typically anodized to provide a hard, almostcrystalline structure of aluminum oxide on the surface of the aluminum.The oxide is tightly formed and becomes, in effect, a barrier to entryof other materials. Anodizing involves the immersion of the part in anelectrolyte solution while a current is passed through the solution andthe part. As oxygen is formed on the anode (the positive terminal whichis the part) it reacts with the part to form a thin layer of aluminumoxide on the surface. After anodizing the part can be soaked in dyewhich penetrates the still porous (relatively) layer of aluminum oxide.The final step is sealing the oxide layer by immersion in boiling water.Further details are found in Electrochemistry Encyclopedia,http:electrochem.cwru.edu/ed/encycl/art-a02-anodizing.htm. Its entiredisclosure is hereby incorporated by reference.

Anodizing aluminum or other metals provides a hard, thin barrier oxidelayer that has many advantages. The barrier oxide layer is usuallyelectrically insulating and has a relatively high dielectric constantcompared to the metal from which it is formed. Aluminum oxide does nothave the high thermal conductivity of aluminum. However, the rate ofheat dissipation depends not only on the inherent conductivity of amaterial, but also its thickness. Since the layer of aluminum oxideneeded for electrical insulation is relatively thin when compared to thealuminum heat sink, the thin aluminum oxide layer does not materiallyimpair the overall thermal conductivity of the aluminum/aluminum oxidesubstrate. In a typical embodiment of the invention, the ratio ofaluminum to aluminum oxide is about 10 to 1.

Hard, barrier oxide may also be created with silicon. It is also wellknown that silicon will oxidize to provide an oxide layer on the surfaceof silicon. This native oxide of silicon is one of its many advantagesin forming integrated circuits. The silicon oxidation process proceedsin a diffusion-like matter so that oxygen atoms attach to silicon atomsand thus will take on the corresponding structure of the siliconsubstrate. If the substrate is crystalline or polycrystalline, thesilicon dioxide layer will have a similar surface. Silicon dioxide is acommon dielectric in semiconductor applications.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

What is claimed is:
 1. A power module package comprising: a powercircuit element having one or more power semiconductor devices; acontrol circuit element electrically connected with the power circuitelement, for controlling the power semiconductor devices within thepower circuit element; a lead frame having external connection terminalleads with inner ends and outer ends and having a first surface to whichthe power circuit element and the control circuit element are attachedand having a second surface opposite the first surface; a metal/metaloxide substrate having a heat sink of a plate of metal and an electricalinsulation layer formed at least on an upper surface of the metal plateand comprising an oxide of the metal, a thermally conductive adhesivefor attaching the electrical insulation layer to part or all of a regionof the second surface of said lead frame that corresponds to a region onthe first surface of said lead frame where the power circuit element isattached; and an encapsulating resin for enclosing the power circuitelement, the control circuit element, the lead frame, and themetal/metal oxide substrate, and outer end of external connectionterminal leads of the lead frame.
 2. The power module package of claim1, wherein the metal is aluminum or aluminum alloy.
 3. The power modulepackage of claim 1, wherein the thermally conductive adhesive comprisesa filler having a high thermal conductivity and an electric insulationproperty.
 4. The power module package of claim 3, wherein the filler isone or more of the group consisting of a nitride, an aluminum oxide, aberyllium oxide, a silicon oxide or a compound of these oxides.
 5. Thepower module package of claim 1, wherein the lead frame furthercomprises a down-set die pad and the power circuit element and theinsulation layer are attached to the down-set die pad.
 6. The powermodule package of claim 1, wherein the insulation layer is formed on afront side of the heat sink.
 7. The power module package of claim 1,wherein the encapsulating resin exposes a rear surface of themetal/metal oxide substrate.
 8. The power module package of claim 1,wherein the metal plate has a second oxide layer formed on its othersurface.
 9. The power module package of claim 1 wherein the lead framecomprises an upper wiring layer.